Question

What is a co-prime number?

Answer 1

Hint: First, we will need to know about the prime numbers and composite numbers.
Prime numbers are the numbers that are divisible by themselves and $1$ only or also known as the numbers whose factors are the given number itself.
But the composite numbers which are divisible by themselves and $1$ and also with some other numbers (at least one number other than $1$ and itself)

Complete step by step answer:
The co-prime numbers are the set of numbers where the common factor among them is one, which is also known as the greatest common divisor is one or the relatively prime numbers. Hence the HCF should be one for those given numbers.
GCD and HCF are the same concepts, where both of them are to find the common divisors or factors and then to find the greatest number among them.
Thus, the co-prime is relatively prime where the GCD or HCF of the two numbers are $1$
Take the numbers $2,4$ and then GCD is $\gcd (2,4) = 2$ because two is the greatest common multiple and hence which is not the co-prime number.
Take the number $2,3$ and then the GCD is $\gcd (2,3) = 1$ because there is no common divisor except the number $1$ and which is the co-prime number. $1$ is co-prime for every number

Note:
We can find whether the given number is prime or composite by the trial-and-error methods. Divide the number with the prime numbers less than the given number. if the number is exactly divisible by the prime number, it is the composite number, if not then it is the prime number.
The only even prime number is $2$ and all other prime numbers are odd.